There have been thin-film solar cells including a light absorbing layer using CuInSe2 being a compound-semiconductor thin film of a chalcopyrite structure composed of a Group-Ib, a Group-IIIb, and a Group-VIb element (that is a CIS-based thin film), or Cu(In,Ga)Se2 being a solid solution thereof with Ga as a solute (that is a CIGS-based thin film). They have been adapted for high efficiencies of energy conversion with reduced deteriorations of efficiency such as due to light irradiation, as an advantage.
For CIS-based thin films being a compound-semiconductor thin film of chalcopyrite structure, or for CIGS-based thin films being a solid solution thereof with Ga as a solute, typically implemented has been a film formation at 550° C. in view of a film quality not to be deteriorated and leak currents not to be increased. It has been considered that at lower temperatures than 550° C. the formation would produce smaller particle diameters, degrading dark current characteristics. It is noted that semiconductor integrated circuits have heat resistant limits about 400° C.
There have been literatures (cf. e.g. Patent Literature 1) disclosing solid-state imaging devices including thin film transistors as switching elements formed on a substrate, and an amorphous semiconductor layer as a sensor region laminated thereon, with interposed pixel electrodes connected to the switching elements, as well as solid-state imaging devices having the above-noted substrate made up by an insulating substrate.
According to the Patent Literature 1, those solid-state imaging devices have the amorphous semiconductor layer employed as a photo sensor region, rendering target wavelengths of photoelectric conversion mostly within a visible wavelength band.
Patent Literature 1: Japanese patent Application Laying-Open Publication No. 2001-144279